microsoft trackball middle mouse button?

[Cow Loon]

I'm trying to use my external trackball mouse to send a middle mouse button click to blender, but the intellipoint software doesn't offer an assignment for middle mouse button. Do you know of a way to get the the scroll wheel button to generates a middle mouse button click, or to get blender to interpret "autoscroll" or something like it, to be middle mouse button? Note that I don't want to do something else like holding down keys while clicking in order to get a middle mouse button click.

[DeltaMac]

USB OverDrive

[Cow Loon]

Thanks! I had to remove the intellipoint software, even thought I had disabled it for blender, before I could get it to work, but it works well.